The SPF (Sun Protection Factor) measured on human skin is recognized as a universal index that represents the effects of cosmetics for ultraviolet radiation prevention that prevent sunburn. Furthermore, an evaluation method for achieving highly accurate evaluation of an ultraviolet radiation protection effect in an actual usage environment or under actual usage conditions has been known (see, for example, Patent Document 1).
According to the technique illustrated in Patent Document 1, a change over time in a spectral transmission spectrum of a measurement sample in a predetermined wavelength range is measured at predetermined wavelength intervals, the correlation between light exposure time and an erythema effect size per predetermined time obtained by dividing the erythema effect size of the measurement sample by an erythema effect size per 1 MED is determined based on the measured change over time in the spectral transmission spectrum, and the in vitro predicted SPF of the measurement sample is calculated based on the time that a cumulative erythema effect size obtained from the determined correlation through time integration takes before reaching 1 MED.